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Icm/Dot-Independent Entry of Legionella pneumophila into Amoeba and Macrophage Hosts

Bandyopadhyay, Purnima and Xiao, Huifang and Coleman, Hope A. and Price-Whelan, Alexa and Steinman, Howard A. (2004) Icm/Dot-Independent Entry of Legionella pneumophila into Amoeba and Macrophage Hosts. Infection and Immunity, 72 (8). pp. 4541-4551. ISSN 0019-9567. http://resolver.caltech.edu/CaltechAUTHORS:BANiai04

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Abstract

Legionella pneumophila, the causative agent of Legionnaires' disease, expresses a type IVB secretion apparatus that translocates bacterial proteins into amoeba and macrophage hosts. When stationary-phase cultures are used to infect hosts, the type IVB apparatus encoded by the icm/dot genes is required for entry, delay of phagosome-lysosome fusion, and intracellular multiplication within host cells. Null mutants with mutations in icm/dot genes are defective in these phenotypes. Here a new model is described in which hosts are infected with stationary-phase cultures that have been incubated overnight in pH 6.5 buffer. This model is called Ers treatment because it enhances the resistance to acid, hydrogen peroxide, and antibiotic stress beyond that of stationary-phase cultures. Following Ers treatment entry into amoeba and macrophage hosts does not require dotA, which is essential for Legionella virulence phenotypes when hosts are infected with stationary-phase cultures, dotB, icmF, icmV, or icmX. Defective host entry is also suppressed for null mutants with mutations in the KatA and KatB catalase-peroxidase enzymes, which are required for proper intracellular growth in amoeba and macrophage hosts. Ers treatment-induced suppression of defective entry is not associated with increased bacterial adhesion to host cells or with morphological changes in the bacterial envelope but is dependent on protein expression during Ers treatment. By using proteomic analysis, Ers treatment was shown to induce a protein predicted to contain eight tetratricopeptide repeats, a motif previously implicated in enhanced entry of L. pneumophila. Characterization of Ers treatment-dependent changes in expression is proposed as an avenue for identifying icm/dot-independent factors that function in the entry of Legionella into amoeba and macrophage hosts.


Item Type:Article
Additional Information:Copyright © 2004, American Society for Microbiology. Received 6 April 2004/ Returned for modification 19 April 2004/ Accepted 21 April 2004 This research was supported by NSF grant MCB-980992 to H.M.S. and by REU supplements that supported the summer research of H.A.C. and A.P.-W. We thank Howard Shuman, Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, for icm/dot mutant strains and advice on the immunofluorescence entry method, and we thank colleagues at Albert Einstein College of Medicine, including the staff of the Laboratory for Macromolecular Analysis and Proteomics (LMAP) for instruction on the use of LMAP isoelectric focusing and LMAP MALDI-TOF equipment, Frank Macaluso of the Analytical Ultrastructure Laboratory for electron microscopy, Magdia De Jesus for analyses of the electron micrographs, and Anne Bresnick for use of her fluorescence microscope.
Record Number:CaltechAUTHORS:BANiai04
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:BANiai04
Alternative URL:http://dx.doi.org/10.1128/IAI.72.8.4541-4551.2004
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1895
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:22 Feb 2006
Last Modified:26 Dec 2012 08:46

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